Field of the Invention
The present invention relates to a Group III nitride semiconductor light-emitting device characterized by the structure of light-emitting layer. More specifically, the light-emitting layer has a MQW structure in which a plurality of layer units are repeatedly deposited, each layer unit comprising a well layer, a protective layer, and a barrier layer sequentially deposited, and is characterized by the protective layer. The present invention also relates to a method for producing the Group III nitride semiconductor light-emitting device.
Background Art
A MQW structure comprising an InGaN well layer and an AlGaN barrier layer alternately and repeatedly deposited, is widely used as a light-emitting layer of Group III nitride semiconductor light-emitting device. Since the barrier layer is formed of AlGaN, the growth temperature of the barrier layer must be higher than that of the well layer to grow with good crystallinity. Therefore, after the formation of the well layer, it is necessary to raise the temperature, and then grow the barrier layer. However, In is evaporated from the well layer due to heating up, thereby causing reduction in emission performance or variation in emission wavelength. Therefore, a protective layer is provided between the well layer and the barrier layer, which is grown at the same temperature as the growth temperature of the well layer, thereby preventing the evaporation of In.
Japanese Patent Application Laid-Open (kokai) No. 2010-80619 discloses that a protective layer comprises a single AlGaN layer or a layered structure of GaN and AlGaN.
However, when the AlGaN protective layer is grown at the same temperature as employed for the well layer, the layer exhibits low crystal quality so that the carrier confinement effect is reduced or carriers are trapped in the protective layer, resulting in reduction of emission performance.